The present invention relates to an optical information recording and reproducing apparatus which records or reproduces information though relative reciprocal movement of an information recording medium and an optical head which irradiates a light beam to the medium. In the present specification, the term information recording and reproducing apparatus includes apparatus which enable only reproduction of information, only recording of information and both recording and reproduction of information.
Prior art apparatus which record and reproduce information by using a light beam include an optical disk which is a rotating disk-shaped recording medium, an optical card which is a reciprocally moved card-shaped recording medium and an optical tape. Those apparatus have their own characteristics and are selectively used in accordance with purposes and applications. Among others, the optical card has a wide application because of the characteristics of ease of manufacture, portability and accessability.
There are various ways to scan the optical card by a light beam. A system in which an irradiation position of the light beam is relatively linearly scanned to the medium reciprocally while the beam irradiation position is relatively moved transversely to the direction of the reciprocal movement has a characteristic that a mechanism is simple and an effective space on the medium is large. A conceptual view thereof is shown in FIG. 1, in which numeral 1 denotes an optical card on which information is to be recorded, numeral 1', shown by a hatched area, denotes a record area, numeral 2 denotes lines of recorded information, numeral 3 denotes an optical head of a recording and reproducing apparatus, numeral 4 denotes a light beam emitted from the optical head 3 and irradiated to the optical card 2, an arrow A indicates a direction of relative reciprocal movement of the light beam 4 or the optical head 3 to the optical head 1, and an arrow B indicates a direction which is transverse to the direction of the reciprocal movement.
In the optical information recording and reproducing apparatus which uses the optical card, it is desirable that the number of information bits recorded or reproduced in a unit of time, that is, a transfer rate is large or high. In order to increase the transfer rate, however, it is necessary that the reciprocation speed in the direction A is high. On the other hand, it is desirable that the speed of movement in the direction A is essentially constant during recording or reproduction, because, if the speed of movement changes, the magnitudes of the recording bits may differ even if the light beam is turned on and off at a constant frequency and a complex processing is required to resolve a problem caused thereby.
In the apparatus which records or reproduces the information by relatively reciprocally moving the optical head or the optical card, either the optical head or the optical card is actually reciprocally moved. Since either of them has a mass, a rise-up time is required before the speed reaches a predetermined level after reversal, and a full-down time is required before it stops from the moving state at the constant speed. The processing is complex when the information is to be recorded or reproduced under a non-constant speed.